Sometimes, measuring ROI can feel like trying to count jellybeans in a jar: impossible. You can’t take the jellybeans out of the jar, so you have to estimate—but that’s just a shot in the dark, right?

Wrong.

There’s a simple trick to estimating how many jellybeans are in a jar, and we’re going to tell you:

1. Count the number of jellybeans in a straight line from top to bottom. This gives you the height of the jar in jellybeans. Let’s say you counted 10.

2. Count the number of jellybeans in a straight line around the jar. If you can’t go all the way, simply count halfway and then multiply by two. This is the circumference of the jar. Let’s pretend the answer was 13.

3. Now you just need to remember those volume formulas you learned in school. Let’s assume we’re working with a cylindrical jar. Plug your numbers into that formula and you get about 104 jellybeans!  

If you can estimate how many jellybeans are in a jar, you can calculate ROI on your supplier rebates.

But what are your inputs for that formula? Download this checklist to discover six points you should consider before making your ROI calculations.